HDFS-4885. Improve the verifyBlockPlacement() API in BlockPlacementPolicy.  Contributed by Junping Du


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-2832@1534417 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c -1534417 . for reverting HDFS-4885, which should be committed to trunk.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-2832@1534424 13f79535-47bb-0310-9956-ffa450edef68